Recently, users' concern relating to fuel efficiency (mileage) has risen. People prefer more fuel-efficient driving. Users who purchased vehicles tend to bring complaint and dissatisfaction suspecting malfunction when the fuel efficiency is lower than they expected.
The mileage of a vehicle per unit quantity of the fuel consumption represents the fuel efficiency. The patent literature 1 describes determination between right and wrong by comparing a current mileage with a predetermined target mileage, wherein determined result is informed to the user (driver).
Patent literature 2 discloses a scheme wherein, responsive to a state of fuel efficiency, at least one of intensity and tone for indicating the fuel efficiency is changed. For example, every time the fuel efficiency changes by a predetermined value, the intensity or tone is changed.
Patent literature 3 describes that behavior data of a vehicle is received from a car navigation device, driving attributes (properties) are determined from the behavior data, and distribution of acceleration is statistical processed to perform safety diagnosis. The fuel consumption is obtained from behavior data, and diagnosis is performed with respect to a fuel saving driving. In this method, with the use of a car navigation device, behavior data of the vehicle is transmitted to a driving diagnosis server, so, not only a load on the car navigation device is increased, but also the car navigation device itself needs a design change for use with this system.